At 5 p.m. ET on Wednesday, before the fight was announced, the average three-night stay in a Las Vegas hotel from Aug. 24-Aug. 27 cost $133 a night. By 11 a.m. ET on Thursday, the average cost per night was $233, a rise of 79 percent.

The $262 cost for a night at the Rio on the Friday before the fight is the third-most expensive night of all the dates left in 2017, according to the website.

Before the announcement was made, the Flamingo Las Vegas had an average three-night stay around the fight date of $158. It is now at $272, a 72 percent increase. The Friday night before the fight (Aug. 25) is $274. To stay the Sunday after the fight (Aug. 27), a room only costs $45.

Other hotels that experienced big increases, according to rates on LasVegas.com, which is owned by the Las Vegas Convention and Visitors Authority, were Harrah's (76 percent), the Wynn (70 percent), New York, New York (68 percent) and Treasure Island (60 percent).

At least one person said he got a deal that turned out to be too good to be true.

James McDaniel, a radio host out of Shreveport, Louisiana, said he booked the Lucky Dragon hotel for $260 total for two nights, including all fees, on Hotels.com shortly after the fight was announced.

An hour and 16 minutes later, he said the site sent him an email that said there was a problem with his credit card and his reservation was canceled. When McDaniel went back to look into the two-night fee at the hotel he had previously reserved, it was now $588. McDonald booked another hotel.

"Same card, same website, no changes whatsoever," McDaniel said. "Never had this happen in my eight years of booking hotels for fights in Vegas."